1. Field of the Invention
The present invention relates to a gas analyzing apparatus. More particularly, the present invention relates to a gas analyzing apparatus for introducing a sample gas from a source thereof into an analysis cell of the gas analyzer, and for compensating a pressure sensitivity of the analysis cell. By way of example, the gas analyzer may perform a quantitative analysis of the sample gas.
2. Description of the Prior Art
In order to conduct an analysis of the exhaust gas from an engine of an automobile under conditions such that the analysis is quick, it is remarkably important that the exhaust gas generated by a combustion cycle of the engine is immediately introduced into a gas analyzer. The exhaust gas from a particular combustion cycle must be introduced to the analyzer as it is so that the exhaust gas generated by the engine both before and after the particular combustion cycle is not mixed therewith.
Accordingly, a gas inlet port for an analysis cell of the gas analyzer has been brought as close as possible to an exhaust valve of the engine. The engine provides its exhaust gasses in pulses of gas flow. Thus, in the case where such a manner of introducing the exhaust gas to the analyzer is taken, if a gas pulse arrives at the inlet port of the analysis cell with a pressure of 1 Kgf/cm.sup.2, for example, when a prevailing pressure in the cell is -0.4 Kgf/cm.sup.2, the cell pressure rises to about -0.1 Kgf/cm.sup.2.
Such a change in the pressure of the exhaust gas introduced into the analysis cell leads to a great fluctuation of an indicated quantitative value for the gas as a result of inherent pressure sensitivity of the analysis cell. Accordingly, in order to reduce the influence of such a fluctuation in pressure, conventional gas analyzers have been provided with a pair of pressure regulators 14, 15, as shown in FIG. 3, each branch-connected with a gas-introducing pipe 12 extending from the engine to an analysis cell 13 of the gas analyzer. The pressure regulators 14 and 15 are respectively connected upstream and downstream of the analysis cell 13 to primarily regulate a pressure within the cell. By operation of the pressure regulator 14 upstream of the analysis cell, and simultaneous operation of the pressure regulator 15 on the downstream side when the pressure within the cell cannot be sufficiently regulated by regulator 15 alone, a reduction is provided in the pressure fluctuations within the cell to about 3%, for example, of that otherwise experienced from a change in inlet pressure from 0 Kgf/cm.sup.2 to 1 Kgf/cm.sup.2.
However, problems have occurred with the conventional gas analyzers because the gas-introducing pipe 12 is changed in sectional shape at the branch connection of the pressure regulator 14 on the upstream side of the analysis cell 13. This change in cross sectional shape turns the exhaust gas introduced into the gas analyzer 13 from a laminar condition into a turbulent condition. Also contributing to this change of the exhaust gas to a turbulent condition is a retention of some of the exhaust gas in a branch pipe 16 leading toward the pressure regulator 14. Because of the volume of this branch pipe 16, some of the exhaust gas generated by the engine before and after a particular combustion cycle is retained and is mixed in with the exhaust gas generated by the particular combustion cycle, and the latter exhaust gas cannot be quantitatively analyzed.